The present invention relates to a display apparatus for a vehicle which comprises an image pickup device to pick up a rearward image from a side portion, in a vehicle width direction, of the vehicle, and in particular, relates to the display apparatus for the vehicle which can adjust a position of a formed virtual image by changing an optical path of image information picked up by the image pickup device.
Conventionally, a head-up display device (HUD) which comprises a projector as a light source and a reflector to reflect display information displayed by the projector toward a projection area of a windshield glass of the vehicle, wherein a virtual image of the display information projected onto the projection area by the reflector is superposed on a forward view of the vehicle, is known. It is also known in the above-described HUD device that the virtual image of the display information is formed in front of the windshield glass, not at the projection area of the windshield glass, by changing an optical path of the display information.
Japanese Patent Laid-Open Publication No. 2008-141574 discloses a visual assist apparatus which comprises plural image pickup devices to pick up images in a visual field which is different from a visual field reflecting in a side mirror, a virtual side-mirror image display controller to display virtual side-mirror images at respective positions which correspond to the plural image pickup devices, and a HUD, wherein the virtual side-mirror image and a virtual image of information of the image picked up by the image pickup device which corresponds to this virtual side-mirror image are concurrently displayed on a windshield glass. Japanese Patent Laid-Open Publication No. 2002-019491 discloses a display apparatus which an information acquisition device to acquire information to be recognized by a driver, a display device (HUD) to display the acquired information on a windshield glass, and a visual-line direction detecting device to detect a direction of a driver's visual line, wherein the acquired information is displayed on the windshield glass at or in the vicinity of a position which is located on an axis of the direction of the driver's visual line.
Herein, the safety standards of the Road Transport Vehicle Act were reviewed according to the revision of the international standards regarding the mirror of the automotive vehicle. Consequently, it became possible to use combination of an image pickup camera and a monitor, in place of the mirror for safety confirmation of automotive vehicle, such as a rearview mirror or a side mirror, so that a so-called mirrorless vehicle was allowed to travel on a public road. According this review of the safety standards, while it is required to meet some requirements, such as an angle of a visual field and quality of a monitor image (video) being to be equal to or better than those of the conventional mirror for rearward confirmation, it has been expected to improve the safety due to visual-field expansion, the gas millage (fuel economy) due to aerodynamics improvement, reduction of noises (wind noise), and so on.
In the mirrorless vehicle, a pair of right-and-left rearward cameras are located at positions which correspond to respective arrangement positions of the side mirrors, and images picked up by these cameras are displayed respectively on a special monitor installed at an instrument panel, for example. Herein, when the driver wants to confirm a side-and-rearward view, it is necessary to change the driver's visual line direction from its forward direction (vehicle traveling direction) toward a direction of the special monitor, so that some complex operations are added to the driver, thereby increasing burdens on the driver. Further, the driver's visual line direction needs to be changed from its forward direction (vehicle traveling direction), which is inappropriate for the safety.
By applying the technologies of the above-described patent documents to the mirrorless vehicle, the virtual images of the image information picked up by the right-and-left rearward cameras can be formed at the windshield glass by using the HUD so as to suppress a move of the driver's visual line direction, thereby reducing the burdens on the driver. However, since the mirrorless vehicle has no side mirror (fender mirror) at both sides of a front end of a vehicle body, it is difficult for the driver to intuitively recognize a width of its own vehicle relative to a distance of lanes in the vehicle traveling direction, so that there is a concern that the operability of the vehicle may be deteriorated. This may be true to the vehicle equipped with the side mirrors.
While the visual assist apparatus of the above-described first patent document concurrently displays the virtual side-mirror image and the virtual image of the image pickup device which corresponds to the virtual side-mirror image, it is unclear whether the virtual image of the image information picket up by the image pickup device is formed in front of the windshield glass. Moreover, it is necessary to set the optical path based on a position of an eyeball of the driver which is actually detected and the display position of the virtual image in order to set the virtual-image forming position precisely. However, since nothing about an eyeball position detector or an optical-path changing device is taught in the present patent document, it is difficult to set the virtual-image forming position of the image information picked up based on the eyeball position of the driver having a driving position, and also its changing is impossible, of course.